DURA 3/4 in. Schedule 40 PVC Coupling (25-Pack) MPP429-007 - The Home Depot
Amazon.com: FangKingNo10pcs 3/4" White PVC Pipe Coupling Adapter Pipe Fittings (Slip to Slip) Schedule 40 Easy to Install,and High Tensile for Home or Industrial Use (1 Pack of 10pcs) (0.75 Inch) :
Cantex 3/4 in. PVC Couplings (15-Pack) R6141624M - The Home Depot